Link 3 is connected by turning pairs A and B to sliders 2 and 4 which move along fixed guides a and b. Cross-pieces Ad and Be of sliders 2 and 4 move in cross-shaped slider 5 . Link 1 is connected by turning pair C to link 3 and by a sliding pair to slider 6. Sliders 5 and 6 are connected together by turning pair D. When slider 2 moves along guides a, point C of link 3 describes ellipse p-p with the equation (x²/a²)+(y²/b²)=1 where a=A͞C, b=C͞B. At the same time, straight line t-t envelops the evolute q-q of the ellipse. The equation of the evolute is ((ax)^(2/3))+((by)^(2/3))=(a²-b²)^(2/3).
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